Thermal energy storages can be used to store heat when heat is readily available and to deliver heat in periods of demand.
Several solid state heat storages using concrete or natural rock as storage medium are previously known. However, inefficient or impractical means for charge and discharge of heat is a typical problem of solid state thermal storages.
In patent publication DE 10 2009 036 550 A1 a solid state thermal heat storage is described, having a first part A and a second part B. A pipe system for feeding or taking out heat is arranged through the first part A, for charging or discharging heat by flowing a working medium through the pipe system. The second part B includes a solid state storage medium, which can be concrete, which is loaded or unloaded with thermal energy, i.e. heat. In operation a heat transfer fluid flows in counter flow to the working fluid in the first part A in order to load or unload heat and the heat transfer fluid further flows in separate channels arranged through the second part B in order to unload or load heat, thereby transferring heat between the first part A and the second part B. The second part B contains a number of channels arranged for flow of the heat transfer fluid, the channels are separate from and are arranged a distance away from the first part A. The heat transfer fluid flows by forced or natural convection. The channels add complexity and reduce levels and ranges of stress and displacement that can be handled, thereby limiting the maximum temperature and temperature range, as well as limiting the pressure of the fluid in the channels.
Other prior art solid state heat storages are described in the patent publications DE 10211598, EP 0049669, EP 1544562, EP 2273225, U.S. Pat. No. 3,381,113, U.S. Pat. No. 4,219,074 and CN 100578133. Said patent publications describe thermal storages without a separate heat transfer fluid which can flow by natural convection in order to transfer heat.
The subject matter of the nearest prior art, DE 10 2009 036 550 A1, is described in an article in CSP-today 12 Mar. 2010, where a working temperature up to 400° C. is described. Further, concrete is described as cost effective for thermal heat storage, but all the other elements, including tubes add cost, resulting in a cost for large plants only slightly cheaper than competing technologies. Achieving a more cost efficient heat storage is set forth as a main challenge; another is to charge and discharge heat more rapidly.
The objective of the present invention is to provide a thermal energy storage which is beneficial over the above mentioned technology with respect to the issues mentioned. Further, the thermal heat storage should preferably be:                Feasible for operation at higher temperature and higher fluid pressure, thereby allowing production of electricity in a turbine-generator more efficiently        Be less complex and more compact        Allow adaptation of materials used according to requirement        Facilitating easy maintenance and replacement of parts        Easier to scale up or down to any size of storage        Have increased versatility, feasible for direct connection to heat producing energy plants such as coal power plants, nuclear power plants, waste burning plants and some solar power plants (concentrated solar power) as well as electric grids and electricity producing power plants such as solar power plants, wind power plants and hydro power plants        Be safe against explosions and the environment        Feasible for operation at −70 to +700° C.        Be possible to use virtually anywhere and in any topography        Faster response for charging and discharging energy        Allowing saving peak production that otherwise would overload the grid or be wasted and allowing delivery when the connected source has insufficient production or the energy price is high, over the day, week or season, balancing power supply to power demand.        Allowing a downscaled grid and more optimal operating parameters of the grid, including reducing the grid investments for peak production and transmission infrastructure between regions and nations        Increasing power security and quality        